1. Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for setting up a radio bearer (RB) in a wireless communication system.
2. Related Art
3rd generation partnership project (3GPP) long term evolution (LTE) is an improved version of a universal mobile telecommunication system (UMTS) and is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) that is an evolution of the 3GPP LTE.
An LTE-A system employs new techniques such as carrier aggregation and a relay. The carrier aggregation is used to flexibly extend an available bandwidth. The relay is used to increase a cell coverage and support group mobility and to enable user-centered network deployment.
The relay provides two types of radio interfaces. One is a Uu interface between a relay and a user equipment, and the other is a Uu interface between the relay and a base station. A radio bearer is set up in each radio interface. In order for the user equipment to receive a service from the base station via the relay, two radio bearers need to be set up.
The radio bearer setup may be delayed as the number of radio bearers to be set up increases. This may result in a service delay.
Accordingly, there is a need for a method capable of preventing a radio bearer setup delay in a system employing a relay.